Pintle or poppet valves are well known. For example, it is known to provide a pintle valve between the exhaust manifold and the intake manifold of an internal combustion engine for recirculating a portion of the engine exhaust into the intake air stream. Such a valve is known in the art as an exhaust gas recirculation (EGR) valve.
An EGR valve consists of two basic components, a valve assembly and an actuator. Typically, an actuator includes a position feedback sensor to monitor the degree of openness of the valve. Typical known actuators include linear solenoids, torque motors, stepper motors, and DC motors. The actuator, when coupled with an appropriate logic driver, moves the pintle shaft of the valve assembly to a desired position as commanded by a master engine control module (ECM). The position sensor provides feedback to the ECM on pintle shaft position so that the ECM can adjust the command to the actuator accordingly. When the engine is running, this closed loop control system operates continuously to regulate the correct amount of exhaust gas recirculation under all engine conditions.
Not all EGR valve performance is equal. Some important performance criteria for an EGR valve actuator are high force capability, to overcome carbon deposits on the pintle shaft; fast response to meet frequency-response modulated timing; low manufacturing cost, with few components and easy assembly; and adjustable actuation stroke, to allow an actuator to be used in a plurality of valve applications or sizes.
Solenoid actuators are low in cost but are also very low in force and generally may be driven in one direction only, relying on a spring for the opposite motion, which spring must be overcome by the solenoid, further reducing the available valve-opening force. Torque motors, although operable in both directions, are also force-limited, stroke-limited, and expensive. Stepper motors are response-time limited and force-limited.
DC motors that can meet the cost and size requirements for an EGR application do not have sufficient torque to generate the required amount of force directly and so typically are coupled to a transmission to gain mechanical advantage. With a proper prior art transmission, a DC motor actuator has the most force potential for an EGR valve but generally has the slowest response time of all prior art actuators.
What is needed is a DC motor as a valve actuator coupled with a gear transmission which overcomes many of the performance limitations of prior art actuators.
It is a principal object of the present invention to provide a high force potential for an EGR valve actuator at fast response time with low design, manufacturing, and assembly costs, having an easily adjustable actuation stroke, and being easily adaptable for combination with any of a plurality of pintle valve assemblies.